The present invention relates to a safety device for diagnostic terminals in distributed computer networks, preferably implemented in vehicles, which diagnostic terminal enable direct access to communication busses transmitting information between distributed nodes within the computer network during operation thereof.
Vehicles are nowadays more frequently equipped with distributed computer networks with numerous nodes monitoring different functions in the vehicle and communication between all nodes is obtained using a common communication bus. The communication is preferably implemented in digital form with messages transmitted serially on the communication bus. Each message contain an address, also designated as an identifier, and data to be transmitted to each respective node or nodes having the dedicated address. In certain type of general messages the address could be missing.
With the purpose of performing a diagnostic routine of essential functions and collecting any fault messages stored in the nodes, an external diagnostic may be connected equipment to the system arranged in the vehicle. The diagnostic equipment could in that respect include an interface having a communication protocol being compatible with the communication bus which will enable transmission and reception of messages on the communication bus arranged in the vehicle. In order to obtain a thorough diagnosis an activation of node functions, using the communication bus, may be needed
In order to be able to connect the diagnostic equipment to the communication bus a diagnostic terminal in the vehicle is needed, the terminal establishing connection at least to the communication bus and preferably also to other systems in the vehicle. This diagnostic terminal is conventionally realised by a multi-contact plug, where a limited number of contact pins of the multi-contact plug is connectable to the communication bus. Remaining contact pins are used for monitoring or controlling purposes of other functions within the vehicle, which are not controlled or managed by the nodes connected to the communication bus.
In certain type of vehicle systems dedicated nodes have been implemented, i.e. Gateway-nodes, which nodes connects the diagnostic terminal to the communication link. This kind of Gateway-nodes often includes functions being able to convert data from the diagnostic equipment according to a specific communication protocol used by the diagnostic equipment and to the communication protocol of the communication bus, and vice versa. Some restrictions in form or type of data to be transmitted between the diagnostic equipment and the nodes arranged in the vehicle is often obtained by such Gateway-nodes.
In order to avoid these expensive Gateway-nodes the diagnostic equipment could instead be connected directly to the communication bus in the vehicle. With the purpose to reduce introduction of disturbances to the communication bus it has been proposed to use a dedicated contact pin in the multi-pin plug as an activator which selectively could unlock a direct access to the communication bus. This will require an increase of contact pins in the diagnostic terminal, which results in an increase of cost and an additional potential source for error.
The object of the invention is to prevent short-circuiting of the communication bus used in distributed computer networks, if contact pins in a diagnostic terminal connected to the communication bus should be short circuited. The invention will also prevent misapplication of voltages and other disturbances on the communication bus via the diagnostic terminal. Short-circuiting, incorrect voltages or other disturbances applied on the communication bus could during operation of the vehicle result in essential functions ceasing to operate, which as an example could lead to the engine being shut down.
Another object is to reduce the number of required contact pins in the diagnostic terminal Yet another object is to obtain a protection against unauthorised access via the diagnostic terminal to the communication bus in distributed computer networks.
By the inventive safety device an improved protection against unauthorised access via the diagnostic terminal to the communication bus may obtained, and at the same time the number of contact pins in the diagnostic terminal may reduced, which will improve the reliability of the distributed computer network and reduce potential sources for error during operation of the computer network or during initiation of a diagnostic routine.
Other distinguishing features and advantages of the invention are evident from the following description of preferred embodiments. Which are made by reference to the drawings.